Compost and legume management differently alter soil microbial abundance and soil carbon in semi-arid pastures

Authors: OTUYA, RAEL - Texas Tech University; SLAUGHTER, LINDSEY - Texas Tech University; WEST, CHUCK - Texas Tech University; DEB, SANJIT - Texas Tech University; Acosta-Martinez, Veronica

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2020
Publication Date: 12/14/2020
Citation: Otuya, R., Slaughter, L., West, C., Deb, S., Acosta Martinez, V. 2020. Compost and legume management differently alter soil microbial abundance and soil carbon in semi-arid pastures. Soil Science Society of America Journal. 85(3):654-664. https://doi.org/10.1002/saj2.20215.
DOI: https://doi.org/10.1002/saj2.20215

Interpretive Summary: Farmers may recycle animal wastes to increase the health of pasture soils under livestock production in the semiarid Southern High Plains of Texas. Scientists at Texas Tech University and ARS in Lubbock tested this concept by adding composted animal waste once at a low rate (1.5 tons per acre) to a clay loam soil under pasture. Adding compost increased soil organic matter by 20% and doubled soil microbes after two growing seasons compared to an untreated soil. Additional benefits, such as, more soil microbes, nitrogen and carbon were obtained in fertilized pastures with only grass compared to unfertilized pastures in a mix with alfalfa. Results from this study showed that a single application of composted animal manure, that is widely available in this region, may be used to increase soil health and productivity of pastures.

Technical Abstract: Establishment of improved perennial pasture systems for livestock production has been demonstrated to improve soil health in the semi-arid Texas Southern High Plains (SHP). Use of waste products from other components of the animal production chain, such as applying composted manure from feedlot operations to grazed pastures, may provide an additional means of improving soil health and sustainability of these systems. However, few studies have examined the impact of composted animal manure on the changes in soil microbial communities although they are important indicators of soil health. We investigated the effects of a one-time composted cattle manure application at 3.36 Mg ha-1 on soil microbial community size and structure, soil organic carbon (SOC), total nitrogen (TN), and soil organic matter (SOM) up to 1.5 years after application. We compared pastures consisting of either WW-B. Dahl Old World bluestem grass alone or in mix with alfalfa, each replicated three times in a randomized complete block design established on a Pullman clay loam soil. Results showed that compost application significantly increased SOC by about 4.4 g kg-1 soil within 1.5 years after application. In N-fertilized grass-only pastures, compost addition increased microbial PLFA abundance, SOC, TN, and SOM, but no significant differences were observed between compost treatments in unfertilized pastures containing legumes. Our results show that even a one-time compost addition at a relatively low rate can augment SOC in this semi-arid pasture system after 1.5 years, and that stimulation of soil microbial abundance and soil C and N from compost is more pronounced in fertilized grass-only pastures compared to those with legume establishment.